The type of load here primarily contemplated is a missile weighing roughly 200 kg with a length of about 4 meters and a diameter between approximately 20 and 50 cm. An erectable launching tube of square cross-section, to be loaded with a missile while in its horizontal position, is conventionally provided in the upper part of its interior with slotted guide rails which accommodate hook-type projections or latches in a central area of the missile body serving to anchor the missile within that tube and to facilitate its erection. The latches fit into their guide slots with small clearance, usually on the order of 0.3 mm, so as to make the alignment very critical. Manual orientation is still the best way of insuring that the missile slides in correctly without overstressing any part of its body or of the tube wall. It is also important that the missile be externally supported until its body has been introduced into the tube, in order to prevent the generation of excessive friction between the slotted guide rails and the latches engaged thereby.
Other loads of the same general type require similar handling during alignment with a receptacle therefor or with an object to be coupled thereto.
Attempts to minimize the effect of gravity by suspending such a load from suitable springs have not fully resolved the problem. With a heavy load such as the aforementioned missile, weight-balancing springs would have to be impractically large.